U.S. patent application number 12/171994 was filed with the patent office on 2010-01-14 for rapid thermal processing chamber with shower head.
This patent application is currently assigned to Applied Materials, Inc.. Invention is credited to Wolfgang Aderhold, Aaron Muir Hunter, Alexander N. Lerner, Joseph Michael Ranish, KHURSHED SORABJI.
Application Number | 20100008656 12/171994 |
Document ID | / |
Family ID | 41505261 |
Filed Date | 2010-01-14 |
United States Patent
Application |
20100008656 |
Kind Code |
A1 |
SORABJI; KHURSHED ; et
al. |
January 14, 2010 |
RAPID THERMAL PROCESSING CHAMBER WITH SHOWER HEAD
Abstract
Apparatus and methods for thermally processing a substrate are
provided. A chamber containing a levitating support assembly
configured to position the substrate at different distances from a
plate during the heating and cooling of a substrate. In one
embodiment a plurality of openings on the surface of the plate are
configured to evenly distribute gas across a radial surface of the
substrate. The distribution of gas may couple radiant energy not
reflected back to the substrate during thermal processing with an
absorptive region of the plate to begin the cooling of the
substrate. The method and apparatus provided within allows for a
controllable and effective means for thermally processing a
substrate rapidly.
Inventors: |
SORABJI; KHURSHED; (San
Jose, CA) ; Ranish; Joseph Michael; (San Jose,
CA) ; Aderhold; Wolfgang; (Cupertino, CA) ;
Hunter; Aaron Muir; (Santa Cruz, CA) ; Lerner;
Alexander N.; (San Jose, CA) |
Correspondence
Address: |
DIEHL SERVILLA LLC
77 BRANT AVENUE, SUITE 210
CLARK
NJ
07066
US
|
Assignee: |
Applied Materials, Inc.
|
Family ID: |
41505261 |
Appl. No.: |
12/171994 |
Filed: |
July 11, 2008 |
Current U.S.
Class: |
392/416 ;
392/418; 392/422 |
Current CPC
Class: |
C23C 16/4557 20130101;
C23C 16/45572 20130101; H01L 21/67098 20130101; C23C 16/45512
20130101; H01L 21/67109 20130101; H01L 21/67207 20130101; C23C
16/481 20130101; C23C 16/45565 20130101; H01L 21/67167 20130101;
C23C 16/4404 20130101; C23C 16/4584 20130101; F27B 17/0025
20130101; H01L 21/67115 20130101 |
Class at
Publication: |
392/416 ;
392/418; 392/422 |
International
Class: |
F26B 19/00 20060101
F26B019/00; F26B 3/28 20060101 F26B003/28; F21V 7/00 20060101
F21V007/00 |
Claims
1. A rapid thermal processing apparatus for heating a substrate,
comprising: a chamber; a support for holding the substrate in the
chamber, the substrate having a first face and a second face
opposite the first face; a radiant heat source directing radiant
energy towards the first face of the substrate and configured to be
quickly turned on and off to controllably heat the substrate with a
desired spatial temperature distribution, including a uniform
distribution; at least one pyrometer for measuring the intensity of
radiation over a predetermined wavelength range, the pyrometer
being positioned to receive radiation emitted by the substrate; and
a plate facing the second face of the substrate, the plate
including at least one gas channel coupled to at least one gas
source and to a plurality of openings on a surface of the plate
configured to evenly distribute process gases over the substrate,
the plate having reflective regions that reflect radiation within
the predetermined wavelength range.
2. The apparatus of claim 1, wherein the plate is positioned in
close proximity to the substrate and the plate absorbs at least a
portion of radiation emitted by the wafer.
3. The apparatus of claim 1, wherein the plate extends over an area
greater than that of the substrate.
4. The apparatus of claim 1, wherein the gas channels are
configured to deliver a first gas and a second gas.
5. The apparatus of claim 4, wherein the first gas and the second
gas are mixed in at least one mixing chamber within the gas
channels.
6. The apparatus of claim 4, wherein at least one of the first and
second the gases are reactive.
7. The apparatus of claim 1, wherein the plate has an outer, highly
reflective portion, and an inner portion having an absorptive layer
underlying said outer portion.
8. The apparatus of claim 7, wherein the openings that are
configured to evenly distribute gas across a radial surface of the
substrate promote thermal coupling of the plate to the
substrate.
9. The apparatus of claim 1, wherein the openings are distributed
evenly across the plate.
10. The apparatus of claim 1, wherein the support for mounting the
substrate is a levitating support assembly configured to move the
substrate between an upper position and lower position within the
chamber.
11. The apparatus of claim 10, wherein the levitating support
assembly is magnetically coupled to a stator assembly.
12. The apparatus of claim 11, wherein the stator assembly is
mechanically coupled to an actuator assembly.
13. The apparatus of claim 1, wherein the reflective regions of the
plate are positioned to reflect heat toward at least one
pyrometer.
14. A method for thermally processing a substrate rapidly,
comprising: rapidly heating the substrate by directing a radiant
heat source to a first surface of the substrate; reflecting the
radiant heat towards a second surface of the substrate with a
reflective body positioned proximate to a second surface the
substrate; cooling the substrate by absorbing heat through an
absorptive plate; and directing a process gas through the
absorptive plate to the second surface of the substrate.
15. The method of claim 14, wherein the substrate is supported by a
levitating and rotating substrate support positioned in a
chamber.
16. The method of claim 14, wherein the substrate is disposed above
and proximate a radiant heat source.
17. The method of claim 16, wherein the substrate and the
absorptive plate are separated by different distances during
heating and cooling.
18. The method of claim 17, wherein the heating comprises a time
period of about 2 minutes or less.
19. The method of claim 16, wherein the substrate is positioned
below and proximate the absorptive plate for cooling.
20. The method of claim 19, wherein the cooling comprises a time
period of about 10 seconds or less.
21. The method of claim 14, wherein the process gas is directed
through a plurality of openings on a surface of the absorptive
plate.
22. The method of claim 21, wherein the openings are positioned to
evenly distribute gas across the radial surface of the substrate to
enhance thermal conduction between the substrate and an absorptive
layer of the absorptive plate during cooling.
23. The method of claim 21, wherein the openings are positioned to
distribute gas across the radial surface of the substrate in a
controlled uneven distribution.
24. The method of claim 14, wherein the thermal processing is a
spike annealing process to form a film on the substrate.
Description
BACKGROUND
[0001] Embodiments of the invention relate generally to heat
treatment of semiconductor wafers and other substrates. In
particular, embodiments of the invention relate to rapid thermal
processing of wafers from a radiant source, such as an array of
incandescent lamps.
[0002] The fabrication of integrated circuits from silicon or other
wafers involves many steps of depositing layers, photo
lithographically patterning the layers, and etching the patterned
layers. Ion implantation is used to dope active regions in the
semiconductive silicon. The fabrication sequence also includes
thermal annealing of the wafers for many uses including curing
implant damage and activating the dopants, crystallization, thermal
oxidation and nitridation, silicidation, chemical vapor deposition,
vapor phase doping, thermal cleaning, and other reasons. Although
annealing in early stages of silicon technology typically involved
heating multiple wafers for long periods in an annealing oven,
rapid thermal processing, (RTP) has been increasingly used to
satisfy the ever more stringent requirements for ever smaller
circuit features. RTP is typically performed in single-wafer
chambers by irradiating a wafer with light from an array of
high-intensity lamps directed at the front face of the wafer on
which the integrated circuits are being formed. The radiation is at
least partially absorbed by the wafer and quickly heats it to a
desired high temperature, for example above 600.degree. C., or in
some applications, above 1000.degree. C. The radiant heating can be
quickly turned on and off to controllably and uniformly heat the
wafer over a relatively short period, for example, of a minute or
less, or even a few seconds. RTP chambers are capable of uniformly
heating a wafer at rates of about 50.degree. C./second and higher,
for example, at rates of 100.degree.-150.degree. C./second, and
200.degree.-400.degree. C./second. Typical ramp-down (cooling)
rates in RTP chambers are in the range of 80-150.degree. C./second.
Some processes performed in RTP chambers require variations in
temperature across the substrate of less than a few degrees
Celsius.
[0003] Since rapid thermal processing works on a single
semiconductor each time, optimal heating and cooling means are
necessary for optimal RTP performance. It is desirable to optimize
substrate temperature uniformity during thermal processing of the
substrate. Temperature uniformity provides uniform process
variables on the substrate (e.g. layer thickness, resistivity, etch
depth) for temperature activated steps such as film deposition,
oxide growth and etching. In addition, substrate temperature
uniformity is necessary to prevent thermal stress-induced substrate
damage such as warpage, defect generation and slip. For example, at
1150.degree. C., a center to edge temperature difference on a
four-inch silicon wafer of approximately 5.degree. C. can induce
dislocation formation and slip. Temperature gradients may also be
induced by other sources. For example, a substrate may have
non-uniform emissivity because of spatial modifications to surface
areas or volumes of the substrate. These modifications may include
films that have been patterned by photolithography or locally doped
regions, such as buried layers for bipolar transistors. In
addition, substrate temperature gradients may be induced by
localized gas cooling or heating effects related to processing
chamber design as well as non-uniform endothermic or exothermic
reactions that may occur on the substrate surface during
processing. It would be desirable to provide RTP chambers that
provide improved temperature uniformity.
SUMMARY
[0004] One or more embodiments of the invention are directed to a
rapid thermal processing (RTP) apparatus for heating a substrate.
The RTP chamber may comprise a chamber and a support for holding
the substrate in the chamber, the substrate having a first face and
a second face opposite the first face. A radiant heat source which
directs radiant energy towards the first face of the substrate may
be inside the chamber. The radiant heat source can be configured to
be quickly turned on and off to controllably heat the substrate
with a desired spatial temperature distribution, including a
uniform distribution. The apparatus further includes at least one
pyrometer for measuring the intensity of radiation over a
predetermined wavelength range. The pyrometer may be positioned to
receive radiation emitted by the substrate. The apparatus may also
include a plate which faces the second face of the substrate. The
plate includes at least one gas channel coupled to at least one gas
source and to a plurality of openings on a surface of the plate.
The openings are configured to evenly distribute process gases over
the substrate. The plate has reflective regions that reflect
radiation within the predetermined wavelength range.
[0005] In other embodiments, the plate may be positioned in close
proximity to the substrate. The plate of these embodiments may
absorb at least a portion of radiation emitted by the wafer. In
further embodiments, the plate extends over an area greater than
that of the substrate.
[0006] In one or more embodiments, the gas channels are configured
to deliver a first gas and a second gas. The first and second gases
may be mixed in at least one mixing chamber within the gas channels
before being delivered. Additional configurations may allow for
more than two gases to be delivered simultaneously. The gases may
also be reactive, and can be mixed before or after delivery to the
substrate surface.
[0007] In further embodiments, the plate has an outer, highly
reflective portion, and an inner portion having an absorptive layer
underlying the outer portion. The reflective regions of the plate
can be positioned to reflect heat toward the at least one
pyrometer.
[0008] The openings of some embodiments are configured to evenly
distribute gas across a radial surface of the substrate to promote
thermal coupling of the plate to the substrate. In other
embodiments, the openings are distributed evenly across the
plate.
[0009] Some embodiments have a support for mounting the substrate
being a levitating support assembly. The levitating assembly can be
configured to move the substrate between an upper position and
lower position within the chamber. The levitating support assembly
can also be magnetically coupled to a stator assembly. The stator
assembly can be further mechanically coupled to an actuator
assembly.
[0010] In one or more embodiments, the substrate can be positioned
at various distances from the plate during the heating a cooling
processes. This may allow for custom tailoring the gas flow field
between the plate and the substrate. The distance can be changed
dynamically, thereby modulating the residence times of active
species to affect the substrate surface chemistry.
[0011] Additional embodiments of the invention are directed toward
methods for rapidly thermally processing a substrate. The method
may include rapidly heating the substrate by directing a radiant
heat source to a first surface of the substrate; reflecting the
radiant heat towards a second surface of the substrate with a
reflective body positioned proximate to a second surface the
substrate; cooling the substrate by absorbing heat through an
absorptive plate; and directing a process gas through the
absorptive plate to the second surface of the substrate.
[0012] The heating of the substrate in some embodiments comprises a
time period of about 2 minutes or less. The cooling of the
substrate in other embodiments may be done in a time period of
about 10 seconds or less. In one or more embodiments, the substrate
is positioned below and proximate the plate for cooling. In other
embodiments, the substrate is positioned above the plate.
[0013] Further embodiments direct the process gas through a
plurality of openings on a surface of the absorptive plate. The
openings may be positioned to evenly distribute gas across the
radial surface of the substrate to enhance thermal conduction
between the substrate and an absorptive layer of the absorptive
plate during cooling. The openings may also be positioned to
distribute gas across the radial surface of the substrate in a
controlled uneven distribution.
[0014] The rapid thermal processing technique of various
embodiments comprises a spike annealing process to form a film on
the substrate substrate.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is a simplified isometric view of an embodiment of a
rapid thermal processing (RTP) chamber;
[0016] FIG. 2 is a cross-sectional view of a substrate positioned
proximate an absorptive shower head according to an embodiment;
[0017] FIG. 3 is a bottom plan view of the absorptive shower head;
and
[0018] FIG. 4 is a cross-sectional view taken along line 3-3 in
FIG. 2.
DETAILED DESCRIPTION
[0019] The embodiments described below are generally directed to an
RTP system including a plate incorporating gas distribution outlets
to distribute gas evenly over a substrate to allow rapid and
controlled heating and cooling of the substrate. The plate may be
absorptive, reflective, or a combination of both. As used herein,
rapid thermal processing or RTP refers an apparatus or a process
capable of uniformly heating a wafer at rates of about 50.degree.
C./second and higher, for example, at rates of 100 to 150.degree.
C./second, and 200 to 400.degree. C./second. Typical ramp-down
(cooling) rates in RTP chambers are in the range of 80-150.degree.
C./second. Some processes performed in RTP chambers require
variations in temperature across the substrate of less than a few
degrees Celsius. Thus, an RTP chamber must include a lamp or other
suitable heating system and heating system control capable of
heating at rates of up to 100 to 150.degree. C./second, and 200 to
400.degree. C./second distinguishing rapid thermal processing
chambers from other types of thermal chambers that do not have a
heating system and heating control system capable of rapidly
heating at these rates. In the embodiment shown, the RTP chamber
optionally includes a substrate support that is adapted to levitate
and rotate within the chamber without any contact with the inside
walls of the chamber. The levitating substrate support system,
coupled with the absorptive plate incorporating gas distribution
outlets, enables the flow from the absorptive plate to be tailored
to enhance heating and cooling of the substrate being processed in
the chamber. By providing the ability to modulate the distance
between the absorptive plate with the gas distribution outlets, the
residence time of active species can be changed and the substrate
surface chemistry can be more accurately changed.
[0020] Referring now to FIG. 1, an exemplary embodiment of a rapid
thermal processing chamber 100 is shown. The processing chamber 100
includes a substrate support 104, a chamber body 102, having walls
108, a bottom 110, and a top 112 defining an interior volume 120.
The walls 108 typically include at least one substrate access port
148 to facilitate entry and egress of a substrate 140 (a portion of
which is shown in FIG. 1). The access port may be coupled to a
transfer chamber (not shown) or a load lock chamber (not shown) and
may be selectively sealed with a valve, such as a slit valve (not
shown). In one embodiment, the substrate support 104 is annular and
the chamber 100 includes a radiant heat source 106 disposed in an
inside diameter of the substrate support 104. The radiant heat
source 106 typically comprises a plurality of lamps. Examples of an
RTP chamber that may be modified and a substrate support that may
be used is described in U.S. Pat. No. 6,800,833 and United States
Patent Application Publication No. 2005/0191044, both of which are
incorporated by reference in their entireties. In one embodiment of
the invention, the chamber 100 includes a plate 200 incorporating
gas distribution outlets (described in more detail below) to
distribute gas evenly over a substrate to allow rapid and
controlled heating and cooling of the substrate.
[0021] The plate may be absorptive, reflective, or have a
combination of absorptive and reflective regions. In a detailed
embodiment, the plate may have regions, some within view of the
pyrometers, some outside the view of the pyrometers. The regions
within view of the pyrometers may be about one inch in diameter, if
circular, or other shape and size as necessary. The regions within
view of the probes may be very highly reflective over the
wavelength ranges observed by the pyrometers. Outside the pyrometer
wavelength range and field of view, the plate can range from
reflective to minimize radiative heat loss, to absorptive to
maximize radiative heat loss to allow for shorter thermal
exposure.
[0022] The RTP chamber 100 also includes a cooling block 180
adjacent to, coupled to, or formed in the top 112. Generally, the
cooling block 180 is spaced apart and opposing the radiant heat
source 106. The cooling block 180 comprises one or more coolant
channels 184 coupled to an inlet 181A and an outlet 181B. The
cooling block 180 may be made of a process resistant material, such
as stainless steel, aluminum, a polymer, or a ceramic material. The
coolant channels 184 may comprise a spiral pattern, a rectangular
pattern, a circular pattern, or combinations thereof and the
channels 184 may be formed integrally within the cooling block 180,
for example by casting the cooling block 180 and/or fabricating the
cooling block 180 from two or more pieces and joining the pieces.
Additionally or alternatively, the coolant channels 184 may be
drilled into the cooling block 180.
[0023] The inlet 181A and outlet 181B may be coupled to a coolant
source 182 by valves and suitable plumbing and the coolant source
182 is in communication with the controller 124 to facilitate
control of pressure and/or flow of a fluid disposed therein. The
fluid may be water, ethylene glycol, nitrogen (N.sub.2), helium
(He), or other fluid used as a heat-exchange medium.
[0024] In the embodiment shown, the substrate support 104 is
optionally adapted to magnetically levitate and rotate within the
interior volume 120. The substrate support 104 shown is capable of
rotating while raising and lowering vertically during processing,
and may also be raised or lowered without rotation before, during,
or after processing. This magnetic levitation and/or magnetic
rotation prevents or minimizes particle generation due to the
absence or reduction of moving parts typically required to
raise/lower and/or rotate the substrate support.
[0025] The chamber 100 also includes a window 114 made from a
material transparent to heat and light of various wavelengths,
which may include light in the infra-red (IR) spectrum, through
which photons from the radiant heat source 106 may heat the
substrate 140. In one embodiment, the window 114 is made of a
quartz material, although other materials that are transparent to
light maybe used, such as sapphire. The window 114 may also include
a plurality of lift pins 144 coupled to an upper surface of the
window 114, which are adapted to selectively contact and support
the substrate 140, to facilitate transfer of the substrate into and
out of the chamber 100. Each of the plurality of lift pins 144 are
configured to minimize absorption of energy from the radiant heat
source 106 and may be made from the same material used for the
window 114, such as a quartz material. The plurality of lift pins
144 may be positioned and radially spaced from each other to
facilitate passage of an end effector coupled to a transfer robot
(not shown). Alternatively, the end effector and/or robot may be
capable of horizontal and vertical movement to facilitate transfer
of the substrate 140.
[0026] In one embodiment, the radiant heat source 106 includes a
lamp assembly formed from a housing which includes a plurality of
honeycomb tubes 160 in a coolant assembly (not shown) coupled to a
second coolant source 183. The second coolant source 183 may be one
or a combination of water, ethylene glycol, nitrogen (N.sub.2), and
helium (He). The housing walls 108, 110 may be made of a copper
material or other suitable material having suitable coolant
channels formed therein for flow of the coolant from the second
coolant source 183. The coolant cools the housing of the chamber
100 so that the housing is cooler than the substrate 140. Each tube
160 may contain a reflector and a high-intensity lamp assembly or
an IR emitter from which is formed a honeycomb like pipe
arrangement. This close-packed hexagonal arrangement of pipes
provides radiant energy sources with high power density and good
spatial resolution. In one embodiment, the radiant heat source 106
provides sufficient radiant energy to thermally process the
substrate, for example, annealing a silicon layer disposed on the
substrate 140. The radiant heat source 106 may further comprise
annular zones, wherein the voltage supplied to the plurality of
tubes 160 by controller 124 may varied to enhance the radial
distribution of energy from the tubes 160. Dynamic control of the
heating of the substrate 140 may be effected by the one or more
temperature sensors 117 adapted to measure the temperature across
the substrate 140.
[0027] In the embodiment shown, an optional stator assembly 118
circumscribes the walls 108 of the chamber body 102 and is coupled
to one or more actuator assemblies 122 that control the elevation
of the stator assembly 118 along the exterior of the chamber body
102. In one embodiment (not shown), the chamber 100 includes three
actuator assemblies 122 disposed radially about the chamber body,
for example, at about 120.degree. angles about the chamber body
102. The stator assembly 118 is magnetically coupled to the
substrate support 104 disposed within the interior volume 120 of
the chamber body 102. The substrate support 104 may comprise or
include a magnetic portion to function as a rotor, thus creating a
magnetic bearing assembly to lift and/or rotate the substrate
support 104. In one embodiment, at least a portion of the substrate
support 104 is partially surrounded by a trough (not shown) that is
coupled to a fluid source 186, which may include water, ethylene
glycol, nitrogen (N.sub.2), helium (He), or combinations thereof,
adapted as a heat exchange medium for the substrate support. The
stator assembly 118 may also include a housing 190 to enclose
various parts and components of the stator assembly 118. In one
embodiment, the stator assembly 118 includes a drive coil assembly
168 stacked on a suspension coil assembly 170. The drive coil
assembly 168 is adapted to rotate and/or raise/lower the substrate
support 104 while the suspension coil assembly 170 may be adapted
to passively center the substrate support 104 within the processing
chamber 100. Alternatively, the rotational and centering functions
may be performed by a stator having a single coil assembly.
[0028] An atmosphere control system 164 is also coupled to the
interior volume 120 of the chamber body 102. The atmosphere control
system 164 generally includes throttle valves and vacuum pumps for
controlling chamber pressure. The atmosphere control system 164 may
additionally include gas sources for providing process or other
gases to the interior volume 120. The atmosphere control system 164
may also be adapted to deliver process gases for thermal deposition
processes, thermal etch processes, and in-situ cleaning of chamber
components. The atmosphere control system works in conjunction with
the showerhead gas delivery system.
[0029] The chamber 100 also includes a controller 124, which
generally includes a central processing unit (CPU) 130, support
circuits 128 and memory 126. The CPU 130 may be one of any form of
computer processor that can be used in an industrial setting for
controlling various actions and sub-processors. The memory 126, or
computer-readable medium, may be one or more of readily available
memory such as random access memory (RAM), read only memory (ROM),
floppy disk, hard disk, or any other form of digital storage, local
or remote, and is typically coupled to the CPU 130. The support
circuits 128 are coupled to the CPU 130 for supporting the
controller 124 in a conventional manner. These circuits include
cache, power supplies, clock circuits, input/output circuitry,
subsystems, and the like.
[0030] In one embodiment, each of the actuator assemblies 122
generally comprise a precision lead screw 132 coupled between two
flanges 134 extending from the walls 108 of the chamber body 102.
The lead screw 132 has a nut 158 that axially travels along the
lead screw 132 as the screw rotates. A coupling 136 is coupled
between the stator 118 and nut 158 so that as the lead screw 132 is
rotated, the coupling 136 is moved along the lead screw 132 to
control the elevation of the stator 118 at the interface with the
coupling 136. Thus, as the lead screw 132 of one of the actuators
122 is rotated to produce relative displacement between the nuts
158 of the other actuators 122, the horizontal plane of the stator
118 changes relative to a central axis of the chamber body 102.
[0031] In one embodiment, a motor 138, such as a stepper or servo
motor, is coupled to the lead screw 132 to provide controllable
rotation in response to a signal by the controller 124.
Alternatively, other types of actuators 122 may be utilized to
control the linear position of the stator 118, such as pneumatic
cylinders, hydraulic cylinders, ball screws, solenoids, linear
actuators and cam followers, among others.
[0032] The chamber 100 also includes one or more sensors 116, which
are generally adapted to detect the elevation of the substrate
support 104 (or substrate 140) within the interior volume 120 of
the chamber body 102. The sensors 116 may be coupled to the chamber
body 102 and/or other portions of the processing chamber 100 and
are adapted to provide an output indicative of the distance between
the substrate support 104 and the top 112 and/or bottom 110 of the
chamber body 102, and may also detect misalignment of the substrate
support 104 and/or substrate 140.
[0033] The one or more sensors 116 are coupled to the controller
124 that receives the output metric from the sensors 116 and
provides a signal or signals to the one or more actuator assemblies
122 to raise or lower at least a portion of the substrate support
104. The controller 124 may utilize a positional metric obtained
from the sensors 116 to adjust the elevation of the stator 118 at
each actuator assembly 122 so that both the elevation and the
planarity of the substrate support 104 and substrate 140 seated
thereon may be adjusted relative to and a central axis of the RTP
chamber 100 and/or the radiant heat source 106. For example, the
controller 124 may provide signals to raise the substrate support
by action of one actuator 122 to correct axial misalignment of the
substrate support 104, or the controller may provide a signal to
all actuators 122 to facilitate simultaneous vertical movement of
the substrate support 104.
[0034] The one or more sensors 116 may be ultrasonic, laser,
inductive, capacitive, or other type of sensor capable of detecting
the proximity of the substrate support 104 within the chamber body
102. The sensors 116, may be coupled to the chamber body 102
proximate the top 112 or coupled to the walls 108, although other
locations within and around the chamber body 102 may be suitable,
such as coupled to the stator 118 outside of the chamber 100. In
one embodiment, one or more sensors 116 may be coupled to the
stator 118 and are adapted to sense the elevation and/or position
of the substrate support 104 (or substrate 140) through the walls
108. In this embodiment, the walls 108 may include a thinner
cross-section to facilitate positional sensing through the walls
108.
[0035] The chamber 100 also includes one or more temperature
sensors 117, which may be adapted to sense temperature of the
substrate 140 before, during, and after processing. In the
embodiment depicted in FIG. 1, the temperature sensors 117 are
disposed through the top 112, although other locations within and
around the chamber body 102 may be used. The temperature sensors
117 may be optical pyrometers, as an example, pyrometers having
fiber optic probes. The sensors 117 may be adapted to couple to the
top 112 in a configuration to sense the entire diameter of the
substrate, or a portion of the substrate. The sensors 117 may
comprise a pattern defining a sensing area substantially equal to
the diameter of the substrate, or a sensing area substantially
equal to the radius of the substrate. For example, a plurality of
sensors 117 may be coupled to the top 112 in a radial or linear
configuration to enable a sensing area across the radius or
diameter of the substrate. In one embodiment (not shown), a
plurality of sensors 117 may be disposed in a line extending
radially from about the center of the top 112 to a peripheral
portion of the top 112. In this manner, the radius of the substrate
may be monitored by the sensors 117, which will enable sensing of
the diameter of the substrate during rotation.
[0036] As described herein, the chamber 100 is adapted to receive a
substrate in a "face-up" orientation, wherein the deposit receiving
side or face of the substrate is oriented toward the plate 200 and
the "backside" of the substrate is facing the radiant heat source
106. The "face-up" orientation may allow the energy from the
radiant heat source 106 to be absorbed more rapidly by the
substrate 140 as the backside of the substrate is typically less
reflective than the face of the substrate.
[0037] Although the plate 200 and radiant heat source 106 is
described as being positioned in an upper and lower portion of the
interior volume 120, respectively, the position of the cooling
block 180 and the radiant heat source 106 may be reversed. For
example, the cooling block 180 may be sized and configured to be
positioned within the inside diameter of the substrate support 104,
and the radiant heat source 106 may be coupled to the top 112. In
this arrangement, the quartz window 114 may be disposed between the
radiant heat source 106 and the substrate support 104, such as
adjacent the radiant heat source 106 in the upper portion of the
chamber 100. Although the substrate 140 may absorb heat readily
when the backside is facing the radiant heat-source 106, the
substrate 140 could be oriented in a face-up orientation or a face
down orientation in either configuration.
[0038] Further details on an absorptive plate 200 are shown in
FIGS. 2 and 3. Referring to FIG. 2, an absorptive plate 200
incorporating gas distribution outlets to distribute gas evenly
over a substrate to allow rapid and controlled heating and cooling
of the substrate is shown. The plate 200 includes a top portion 201
having a gas introduction system 202, includes a first gas
introduction port 204 and an optional second gas introduction port
206 in communication with a gas mixing chamber 208 for mixing gases
the two gases. If only a single gas introduction port is provided,
mixing chamber 208 can be eliminated from the design. It will be
understood that additional gas introduction ports can be provided
as well. The gas introduction ports 202, 204 would of course be
connected to a suitable gas source such as a tank of gas or gas
supply system (not shown). Mixing chamber 208 is in communication
with gas flow passage 212, which is in communication with gas
channel 214 and gas introduction openings 216 formed in blocker
plate 213. The blocker plate 213 may be a separate component
fastened to the top portion 201, or it may be integrally formed
with the top portion. Of course, other designs are possible,
including ones where two or more sets of individual openings of the
type 216 are provided for two or more gases so that gas mixing
takes place after exiting the showerhead. The absorptive plate
includes a face 203 through which openings 216 are formed.
[0039] FIG. 3 shows a plan view of an absorptive plate 200 and the
plurality of openings 216 through face 203. It will be understood
that the number of and pattern of openings can be varied and the
design shown in FIG. 3 is exemplary only. For ease of illustration,
bores through the plate 200 to allow the temperature sensors 117 to
measure the temperature of the substrate. In one or more
embodiments, the plurality of openings on the absorptive plate
comprise of no more than 10% of the plate's surface. In one
embodiment the plurality of openings are positioned no closer than
within a 25 mm of the pyrometers and within a 1 in diameter of the
highly reflective surface of the absorptive plate.
[0040] In one or more embodiments, in a system for processing
silicon substrates, a pyrometer that detects long radiation
wavelengths (e.g., wavelengths greater than about 3.5 to 4 microns)
is utilized as the temperature sensor 117. However, this approach
is best suited for temperatures above 700.degree. C. At room
temperature, a silicon wafer is transparent to wavelengths of light
longer than 1.0 microns. As the temperature of the substrate
increases, the substrate becomes opaque to the longer wavelengths
until, at about 700.degree. C., the substrate becomes opaque to all
wavelengths of interest. Thus, at temperatures below 700.degree.
C., a long wavelength sensitive pyrometer will be more apt to also
detect light coming directly from the heat source. In short, the
wavelength sampled by the pyrometer will typically vary with the
process temperature. If the process temperature is substantially
below 700.degree. C., then the pyrometer will typically sample
wavelengths shorter than 1.1 microns. If higher process
temperatures are used, then longer wavelengths can be sampled.
[0041] In one design, particularly suitable for process
temperatures between 900.degree. C. and 1350.degree. C., a
solid-state pyrometer is used that is sensitive to radiation at
wavelengths between 0.9 microns and 1.0 microns. In this
temperature range, there is substantial amount of radiation
produced in the wavelength range 0.9-1.0 microns providing high
signal strengths and high signal-to-noise ratios.
[0042] FIG. 4 shows a layering arrangement that may be used on the
absorptive plate 200. As shown in FIG. 4, the face 203 of the
absorptive plate 200 that faces the substrate 140 during processing
has a layer that is highly reflective of radiation in a target
wavelength range and less reflective of radiation outside the
target wavelength range. In some embodiments, one or more coatings
or layers are provided on the absorptive plate surface to achieve
this selective reflectivity. In one embodiment, these coatings
provide high reflectivity for radiation in the target wavelength
range, and include one or more interference layers positioned over
the surface of the absorptive plate.
[0043] As shown in FIG. 3, one or more interference layers 250 are
included in the layer structure. The interference layers contain
pairs of layers, each pair comprising a layer with a low index of
refraction and a layer with a high index of refraction. Together,
the interference layers comprise a structure that is highly
reflective of radiation in the target wavelength range and less
reflective of radiation outside the target wavelength range. The
particular material, thickness, and other characteristics of the
interference layers are selected based on a number of
characteristics of the processing system, including the target
wavelength range desired. A suitable interference layer structure
may be obtained from Research Electro-Optics, Inc, of Boulder,
Colo.
[0044] In one embodiment, a highly reflective portion of an
absorptive plate 200 comprises a quarter-wave stack. The
quarter-wave stack is made up of alternating dielectric layers
which have different indices of refraction and have optical
thickness equal to 1/4 of the wavelength to which the pyrometer is
most sensitive over the respective angles of acceptance into the
pyrometer (e.g., a thickness equal to 1/4 of 950 nanometers). As
noted above, the interference layers 250 provide high reflectivity
for radiation in the target wavelength Another portion of the
absorptive plate 200 absorbs radiation outside the target
wavelength. In one embodiment, an absorptive layer 252 can be
positioned above the absorptive plate's face 203 and below the
interference layers 250. This absorptive layer 250 is more
absorptive than the high reflectivity portion of the absorptive
plate 200. As radiation outside the target wavelength passes
through the interference layers, it is absorbed by the absorptive
layers. The resultant heat passes through the absorptive plate 200
and is dissipated through the cooling mechanism described
above.
[0045] Various materials may be employed for the absorbing layer
252 including, for example, metal oxides, and suitable materials
will be apparent to those of skill in the art. Moreover, other
mechanisms for absorption of radiation may also be employed. For
example, rather than employing an absorbing layer 252 as shown in
FIG. 4, the absorptive plate face 203 may absorb radiation that
passes through the highly reflective portion of absorptive plate.
Likewise, the structure of the interference layers 250 shown in
FIG. 4 is merely exemplary; other mechanisms known in the art may
be used to filter, mirror, or reflect radiation in the target
wavelength range away from the absorbing portion of the absorptive
plate 200.
[0046] As shown in FIG. 4, a passivation layer 254 may be employed
above the interference layers 250. This passivation layer prevents
the material of the layers above the absorptive plate face 203 from
possibly contaminating the chamber. The passivation layer 254 may
be made of silicon dioxide, aluminum oxide, silicon nitride, or any
other acceptable material that will passivate the reflector without
unacceptably degrading its reflective properties in the wavelength
range of interest.
[0047] Other layers 256, 258 may be employed on the reflector
surface within the scope of the present invention to perform
well-known functions for the fabrication or operation of the
device. For example, such layers 256, 258 may be employed to
facilitate application of, or transition between, the absorbing
layer 252, the interference layers 250, and/or the passivation
layer 254.
[0048] Generally the target wavelength range corresponds to the
spectral region that is used for the pyrometric temperature
measurement. In one embodiment, the pyrometric temperature
measurement is an optical measurement of the radiation emitted by
the substrate within a narrow spectral region. This spectral region
is preferably approximately between 700 and 1000 nanometers.
Similarly, the wavelength of radiation to be absorbed can also be
identified. The spectrum of the radiated energy from a substrate
during thermal processing is a complicated function of temperature,
emissivity, and Planck's blackbody law. In simplified terms, the
spectral limits of the absorbing portion of the reflector are
determined by the blackbody law and the temperature range of the
peak temperature of the process, i.e., the temperature of the
process where radiative cooling is most desired.
[0049] In a detailed embodiment, shown in FIG. 3, an absorptive
plate 200 has regions 205 of about one inch in diameter on each of
the probes through which the temperature sensors, which are
typically pyrometers, can measure the intensity of radiation over a
predetermined wavelength region. The regions 205 have very high
reflectivity over the pyrometer wavelength range, which may be in
the form of a multi-layer dielectric stack over a specular surface
in the regions 205 The main importance of these regions is that
they provide a local region where there is significant enhancement
of the apparent emissivity of the wafer in the region as viewed by
the pyrometer.
[0050] In the embodiment shown in FIG. 1, the separation between
the substrate and the plate 200 is dependent on the desired thermal
exposure for the given substrate. In one embodiment, the substrate
can be disposed at a greater distance from the plate 200 and closer
to the lamps to increase the amount of thermal exposure of the
substrate and to decrease the cooling from the plate. When the
substrate is placed at position closer to the plate 200 and further
from the lamps, this configuration decreases the amount of thermal
exposure of the substrate and increases the cooling received from
the plate. The exact position of the substrate during the heating
of the substrate and the residence time spent in a specific
position is conditional on the desired amount of thermal exposure
and amount of cooling. In most cases, the residence time is
dependent on the desired surface chemistry of the substrate. The
embodiment shown in FIG. 1 allows the substrate support to be
easily levitated at different vertical positions inside the chamber
to permit control of the substrate's thermal exposure.
[0051] In an alternative embodiment, the absorptive plate and light
source are inverted from the configuration shown in FIG. 1. In the
inverted configuration, when the substrate is proximate the
absorptive plate, the thermal conduction from the substrate to the
absorptive plate 200 will increase and enhance the cooling process.
The increased rate of cooling in turn can promote optimal RTP
performance. Thus, when the substrate is positioned closer to the
absorptive plate, the amount of thermal exposure to the lamps
decreases while the amount of cooling from the plate increases.
[0052] In one embodiment, as the substrate is moved into a position
proximate an absorptive plate, a gas can be released from a
plurality of openings found on the surface of the absorptive plate
to optimize cooling of the substrate. The plurality of openings may
be configured to evenly distribute the gas across the radial
surface of the substrate to enhance thermal conduction and
convection between the substrate and the absorptive layer of the
absorptive plate. To enhance the conductive effects, a more
conductive gas may replace a less conductive gas, or the velocity
of gas passing through holes 216 could be increased, creating
turbulence and enhancing convective coupling between the showerhead
and the substrate. Distributing gas radially towards the substrate
optimizes cooling of the substrate and optimizes spike performance
of the RTP chamber. In some embodiments, the substrate support can
rotate the substrate to promote even distribution of gas over the
substrate during processing for better uniformity.
[0053] A method from thermally processing a substrate inside a RTP
chamber involves positioning a substrate at a desired distance from
the absorptive plate. The substrate can be easily moved to
positions that are ideal for heating and cooling the substrate as
set forth by the specifications for thermal processing. The
substrate moves at different distances from the absorptive plate by
utilizing the levitating support assembly described above. In one
embodiment, the support assembly can be controlled by a CPU
attached to the RTP chamber.
[0054] In another embodiment, a different set of gases can be
utilized during thermal processing. One set of gases are used
during the heating of the substrate and a second set of gases are
used during the cooling of the substrate. The selections of gases
are dependent on the desired thermal conductivity. For example,
using a low conductivity gas during thermal processing will
decrease the amount of energy required during the ramp while using
a gas of high thermal conductivity at the end of the process will
increase the cool down rate.
[0055] Accordingly, one or more embodiments of the invention are
directed to a rapid thermal processing (RTP) apparatus for heating
a substrate. The RTP chamber may comprise a chamber and a support
for holding the substrate in the chamber, the substrate having a
first face and a second face opposite the first face. A radiant
heat source which directs radiant energy towards the first face of
the substrate may be inside the chamber. The radiant heat source
can be configured to be quickly turned on and off to controllably
heat the substrate with a desired spatial temperature distribution,
including a uniform distribution. The apparatus further includes at
least one pyrometer for measuring the intensity of radiation over a
predetermined wavelength range. The pyrometer may be positioned to
receive radiation emitted by the substrate. The apparatus might
also include a plate which faces the second face of the substrate.
The plate includes at least one gas channel coupled to at least one
gas source and to a plurality of openings on a surface of the
plate. The openings are configured to evenly distribute process
gases over the substrate. The plate has reflective regions that
reflect radiation within the predetermined wavelength range.
[0056] In other embodiments, the plate may be positioned in close
proximity to the substrate. The plate of these embodiments may
absorb at least a portion of radiation emitted by the wafer. In
further embodiments, the plate extends over an area greater than
that of the substrate.
[0057] The gas channels of various embodiments are configured to
deliver a first gas and a second gas. The first and second gases
may be mixed in at least one mixing chamber within the gas channels
before being delivered. Additional configurations may allow for
more than two gases to be delivered simultaneously. The gases may
also be reactive, and can be mixed before or after delivery to the
substrate surface. "Reactive gases" refer to gases that may be used
for a reaction on the substrate such as an etching gas, or gases
that are precursors that are used to form a material on the
substrate.
[0058] In further embodiments, the plate has an outer, highly
reflective portion, and an inner portion having an absorptive layer
underlying the outer portion. The reflective regions of the plate
can be positioned to reflect heat toward the at least one
pyrometer.
[0059] The openings of some embodiments are configured to evenly
distribute gas across a radial surface of the substrate to promote
thermal coupling of the plate to the substrate. In other
embodiments, the openings are distributed evenly across the
plate.
[0060] Some embodiments have a support for mounting the substrate
being a levitating support assembly. The levitating assembly can be
configured to move the substrate between an upper position and
lower position within the chamber. The levitating support assembly
can also be magnetically coupled to a stator assembly. The stator
assembly can be further mechanically coupled to an actuator
assembly.
[0061] In one or more embodiments, the substrate can be positioned
at various distances from the plate during the heating and/or
cooling processes. This may allow for custom tailoring the gas flow
field between the plate and the substrate. The distance can be
changed dynamically, thereby modulating the residence times of
active species to affect the substrate surface chemistry.
[0062] Additional embodiments of the invention are directed toward
methods for rapidly thermally processing a substrate. The method
may include rapidly heating the substrate by directing a radiant
heat source to a first surface of the substrate; reflecting the
radiant heat towards a second surface of the substrate with a
reflective body positioned proximate to a second surface the
substrate; cooling the substrate by absorbing heat through an
absorptive plate; and directing a process gas through the
absorptive plate to the second surface of the substrate.
[0063] The heating of the substrate in some embodiments comprises a
time period of about 2 minutes or less. The cooling of the
substrate in other embodiments may be done in a time period of
about 10 seconds or less.
[0064] The substrate of various embodiments is positioned below and
proximate the absorptive plate for cooling.
[0065] Further embodiments direct the process gas through a
plurality of openings on a surface of the absorptive plate. The
openings may be positioned to evenly distribute gas across the
radial surface of the substrate to enhance thermal conduction
between the substrate and an absorptive layer of the absorptive
plate during cooling. The openings may also be positioned to
distribute gas across the radial surface of the substrate in a
controlled uneven distribution.
[0066] The rapid thermal processing technique of various
embodiments comprises a spike annealing process to form a film on
the substrate substrate.
[0067] Reference throughout this specification to "one embodiment,"
"certain embodiments," "one or more embodiments" or "an embodiment"
means that a particular feature, structure, material, or
characteristic described in connection with the embodiment is
included in at least one embodiment of the invention. Thus, the
appearances of the phrases such as "in one or more embodiments,"
"in certain embodiments," "in one embodiment" or "in an embodiment"
in various places throughout this specification are not necessarily
referring to the same embodiment of the invention. Furthermore, the
particular features, structures, materials, or characteristics may
be combined in any suitable manner in one or more embodiments.
[0068] Although the invention herein has been described with
reference to particular embodiments, it is to be understood that
these embodiments are merely illustrative of the principles and
applications of the present invention. It will be apparent to those
skilled in the art that various modifications and variations can be
made to the method and apparatus of the present invention without
departing from the spirit and scope of the invention. Thus, it is
intended that the present invention include modifications and
variations that are within the scope of the appended claims and
their equivalents.
* * * * *